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Roadhog

Cornwall help . . .

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I just came into a one owner pair of 1980 Cornwall (C model on the label with the original instruction sheets which call them Cornwall II) speakers in VGC. I demo'd the speakers very briefly, and all sounded well enough given the cheap receiver and room/spacing for the prepurchase test. I bought them, pulled a muscle or two loading/unloading, etc. Installed side by side my with Forte IIs. A/B tests having me wondering if the CWs have an issue. CWs definately have a fuller and wider bottom. Mids seem fine although less defined (colorful?) than the fortes, and finally the highs are lacking across the range and only manage to project if the speaker is aimed almost directly at me and even then, high hats and ride cymbals are almost non-existent out of the CWs. All strings are much more pronounced in the Forte IIs with better definition. I've always found the Forte IIs colorful, but the difference is too big to not be an issue. Where to start? Capacitors? Diaphragms? Something else??

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I think you hit the problem.  Bob Crites is the guy to help you.  He is a long time forum member and sells the parts.  Welcome to the forum and wait for others to chime in on your question.

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Well, start with the basics.  Do both tweeters play? 

 

If so, open the backs and loosen and retighten the screw connections on the crossover.  Did it change?  If yes, you're good, if no, keep going.

 

If the tweeter(s) don't play, disconnect it from the crossover and use a multimeter to check the DC resistance.  A square magnet K-77-M should read right about 7 ohms.  If it's very low, it may be shorted, if extremely high the voice coil is open and it needs a new diaphragm. 

 

Look for loose wires.  Reconnect.  There is a copy of the crossover schematic in the Technical Section.

 

If the tweeter(s) play, but have low output and have good DCR, look to see if there is corrosion on any terminals/connections or it any of the caps leak.  If no, you likely need new caps.  I think Bob Crites and others can measure the caps, but at 35 years old, it wouldn't hurt to replace them with good quality foil caps of your choice.  Match the OEM values with as small a tolerance as you are willing to pay for. 

Edited by John Albright
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Ok, thanks for the prompt replies.

Step 1 . . . No sound from either tweet.

Step 2 . . . Locate a multimeter.

Can't believe I missed this when demoing them. Oh well, I needed a project- and damn are they going to sound nice.

I checked out Crites site. If indeed I just need new diaphragms- are the titanium ones listed ($54) for the CWII the one for the 77M (square magnet)? I'm guessing so.

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36 year old speaker crossover capacitors might just need some attention. There was a world of difference after Dean did mine. And be very careful while operating the screws holding the backs on.

JJK

Edited by JJKIZAK

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Those are in great shape! As John said, loosen and retighten all the screws on the crossover connections, check the tweets with a multimeter (disconnected from the crossover).

 

A guitarist, too! Is that a genuine tele or some other fine make?

 

Welcome to the craziness!

 

Bruce

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Thanks to all. That indeed is a fender telecaster. If I do indeed need diaphragms, I can't tell from BCrites website if they are available or not. There is mention of titanium diaphragms with the CWIIs listed on the Pricing-Other page, but I'm not sure it that is a typo. I do see that BC makes the C125 tweeters as replacements for the whole k77M unit.

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Just give Bob a call....he will help you out. I would replace the caps also while your at it. If you get striped out screw holes when you remove the backs just insert tooth pics with a little glue and it will be all good then.

 They look awesome though.

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Replace the capacitors in the crossover, and replace the k-77 with Bob's CT120... or CT125 if you are on a budget.. There are no good quality diaphragms for the k-77... plus either of Bob's tweeters will easily outperform the k-77. If you want to stay will all original Klipsch driver, let me know, I can sell you a clean pair of K-77's with square magnets just like yours.

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I wonder if that woofer has been taken out of there before and put back rotated a bit. That lead to the crossover looks kinda tight.

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I noticed that too when I open up the box.  The woofer lead looked really snug, but has just a small bit of slack keeping it from being tight.  I haven't opened the other speaker yet to compare.  Is that woofer lead normally very slack?  As for the k77M diaphragms, my only choice appears to be simply speakers $18ea variety which few around these parts recommend.  I had practically sold myself on the idea of swapping to Crites C125s, but I've read some found them to have better range than the k77 but with less output- leaving the highs less alive or present.  The ALK eng K77 replacement option looks interesting, but more expensive.  I'm convinced a crossover rebuild kit is just a good investment at this point as well.  Anyone want to chime in about their experience with the C125s or the ALK eng tweeter alternatives?  I've already read another comparo elsewhere in the forums.

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Those replacement K-77 diaphragms from simply speakers are junk.

 

Unless you can find some new old stock replacements you will be much better off buying a new set of tweeters.

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I used the CT125s in my LaScalas and thought they were a huge improvement while my older son put a pa>r into his or>gina) Heresy speakers, also with great results.

Bruce

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Th Cries tweeters sound great to me...i put in the 4500 crossover mod. on my Ks also. I have put the old round magnet and the crites next to each other and the crites is much better. The old round magnet ones had new diaphrams in them also from Bob when he could still get good ones.

 You could rotate the woofer just a bit to make the wire length better don't forget to loosen and retighten all those screws on the crossover.

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Why the 4500 crossover mod?

JJK

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Takes the load off the mid range driver cause the Crites tweeter can go down lower to meet the 4500 point. I like it but did not A/B it to confirm my opinion I just trusted Bob.

  But that crossover will not work in the Cornwall because of different horn just to be clear.... but the tweeter will work fine.

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